For automatic music playing pianos, in general, performance data which has been recorded on a floppy disk or similar type of data recording media is read out from the media, and according to the data thus read out, key solenoids and pedal solenoids are activated. In the case of automatic playing pedal mechanisms in which the pedals alternate between a fully depressed state and a fully released state, a pedal solenoid which can be controlled between an on state and an off state is ordinarily sufficient. Thus, for recording performance data for this type of 2 mode automatic pedal mechanism, it suffices to detect only the fully depressed and fully released pedal states for the respective pedal. Similarly, during play back of the recorded data, it is sufficient for the pedal to merely switch between on and off states based on the recorded performance data.
In order to improve the music reproduction characteristics, it is necessary to be able to reproduce half pedal states as well as the fully released and fully depressed states. In order to prepare performance data which permits the replaying of half pedal states, it is necessary to continuously detect pedal position during the recording of a performance. By so doing, during automatic playing of a previously recorded performance, the respective pedal reacts only to the extent indicated by the recorded performance data.
With the type of prior art automatic playing pedal mechanism described above, feed back control of the electrical power supplied to the solenoids may be carried out. In the case of such feed back control, pulse width modulation (PWM) is often employed for the solenoid control signals. Additionally, simple control of the voltage and/or current of the control signals is sometimes employed.
In regard to the object of control itself, the piano pedal mechanisms, it is well known that the response characteristics and other mechanical characteristics of the respective pedal mechanisms vary widely from piano to piano. Additionally, each piano has several different types of pedals (for example the loud pedal and the shift pedal), each with different response characteristics and requirements as well. Furthermore, it is difficult to manufacture solenoids with uniform response characteristics. Additionally, the amount of displacement of solenoid plungers does not have a linear relationship with the supplied electrical power.
Because of the above described properties, when a musical performance is recorded on one conventional automatic music playing piano and replayed on another using the recorded performance data, faithful reproduction of the pedal effects of the original piano, and therefore faithful reproduction of the original piano performance cannot be achieved.